A wide variety of liquid dispensing devices that are pressurized to expel the liquid and are of a portable size are presently available on the market and in the literature. An especially common type of portable sprayer widely distributed by garden and hardware stores is a type that has a main opening located at the top and a second opening located on the side. The second opening is small and connected to a hose for spraying the chemical or liquid from the tank under pressure. The main opening is relatively large and the liquid to be dispensed is poured into the container through this opening. The opening is then closed by a cap that is screwed into the opening and includes a hand-pump integral therewith. The hand pump is used to supply air pressure to the inside of the tank to pressurize the liquid to be dispensed therefrom through the small opening and its hose and nozzle. As the liquid is dispensed from the tank, the pressure declines and it is necessary that the hand pump be operated to rebuild the pressure.